Positioning systems are widely used to estimate a receiver's location using positioning signals that the receiver receives from one or more types of beacons (e.g. terrestrial transmitters or satellites). Positioning signals transmitted from satellites can have relatively low power levels which makes those positioning signals susceptible to interference. By contrast, positioning signals from terrestrial transmitters are often received at a receiver at higher power levels. However, the frequencies used to transmit terrestrial positioning signals are not subject to the same use restrictions as more conventional positioning system signals, since the terrestrial transmitters may operate within, or near, an unlicensed frequency band. Low-power emitters (e.g. consumer devices) operating at or near the same frequency band can be a source of interference. This interference may not have a predictable time and/or frequency pattern.
The presence of interference in the frequency bandwidth of interest is a serious problem for receivers. In time-of-arrival (TOA) positioning systems, this interference can degrade the quality of a position estimate made by the receiver. Additionally, this interference can compromise other aspects of signal acquisition and system time synchronization. Thus, solutions are needed to determine and mitigate interference within a positioning system. Different systems and methods for interference detection and mitigation using maximal ratio combining (MRC) in the correlation domain are described in the disclosure that follows.